September 6th, 2013 06:00 AM

Andy Murray, of Great Britain, reacts during a break between sets after losing the first two sets to Stanislas Wawrinka, of Switzerland, during the quarterfinals of the 2013 U.S. Open tennis tournament, Thursday, Sept. 5, 2013, in New York. AP

NEW YORK — Andy Murray’s reign as defending U.S. Open champion ended in a surprising, frustration-filled 6-4, 6-3, 6-2 quarterfinal loss to ninth-seeded Stanislas Wawrinka on Thursday.

After one set, Murray slammed his racket into the court, then mangled it once he reached his chair on the sideline. After the second, he gestured over to his coach, Ivan Lendl, and let out a frustrated scream.

Wawrinka had Murray in knots all day.

ADVERTISEMENT

“I would have liked to have played a little bit better,” Murray said after rushing off the court and into the interview room to explain the loss. “I’ve had a good run the last couple of years. It’s a shame I had to play a bad match today.”

Ninth-seeded Wawrinka made his first Grand Slam semifinal, earning a spot in the final four for Switzerland that for so long felt like Roger Federer’s birthright.

The third-seeded Murray broke into the elite echelon of tennis last year, winning his first Grand Slam tournament at Flushing Meadows, then his second at Wimbledon in June.

But the straight-set loss to Wawrinka ended a stay in New York during which he never got completely comfortable — not when he had to wait until Wednesday night of the first week to begin the defense of the title, not when he struggled in a four-set victory over Denis Istomen in the fourth round and certainly not on Thursday.

This was Murray’s earliest exit from the U.S. Open since 2010, when Wawrinka also did the honors — that year in the third round.

Murray conceded it’s been a long road since he broke into the top, first at the Olympics on home turf last year, then with the two major titles.

“When you work hard at something for a lot of years, it’s going to take time to fire yourself up and get to training 110 percent,” Murray said about his preparation for the year’s final Grand Slam. “That’s something kind of natural after what happened at Wimbledon.”